Unix/Linux/sheepthreads.c

/*
 *  sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
 *                   like nonstandard stacks)
 *
 *  SheepShaver (C) 1997-2002 Christian Bauer and Marc Hellwig
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/*
 *  NOTES:
 *   - pthread_cancel() kills the thread immediately
 *   - Semaphores are VERY restricted: the only supported use is to have one
 *     thread sem_wait() on the semaphore while other threads sem_post() it
 *     (i.e. to use the semaphore as a signal)
 */

#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <sched.h>
#include <pthread.h>
#include <semaphore.h>


/* Thread stack size */
#define STACK_SIZE 65536

/* From asm_linux.S */
extern int atomic_add(int *var, int add);
extern int atomic_and(int *var, int and);
extern int atomic_or(int *var, int or);
extern int test_and_set(int *var, int val);

/* Linux kernel calls */
extern int __clone(int (*fn)(void *), void *, int, void *);

/* struct sem_t */
#define status __status
#define spinlock __spinlock
#define sem_lock __sem_lock
#define sem_value __sem_value
#define sem_waiting __sem_waiting

/* Wait for "clone" children only (Linux 2.4+ specific) */
#ifndef __WCLONE
#define __WCLONE 0
#endif


/*
 *  Return pthread ID of self
 */

pthread_t pthread_self(void)
{
        return getpid();
}


/*
 *  Test whether two pthread IDs are equal
 */

int pthread_equal(pthread_t t1, pthread_t t2)
{
        return t1 == t2;
}


/*
 *  Send signal to thread
 */

int pthread_kill(pthread_t thread, int sig)
{
        if (kill(thread, sig) == -1)
                return errno;
        else
                return 0;
}


/*
 *  Create pthread
 */

struct new_thread {
        void *(*fn)(void *);
        void *arg;
};

static int start_thread(void *arg)
{
        struct new_thread *nt = (struct new_thread *)arg;
        nt->fn(nt->arg);
        return 0;
}

int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine)(void *), void *arg)
{
        struct new_thread *nt;
        void *stack;
        int pid;

        nt = (struct new_thread *)malloc(sizeof(struct new_thread));
        nt->fn = start_routine;
        nt->arg = arg;
        stack = malloc(STACK_SIZE);

        pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM | CLONE_FS | CLONE_FILES, nt);
        if (pid == -1) {
                free(stack);
                free(nt);
                return errno;
        } else {
                *thread = pid;
                return 0;
        }
}


/*
 *  Join pthread
 */

int pthread_join(pthread_t thread, void **ret)
{
        do {
                if (waitpid(thread, NULL, __WCLONE) >= 0);
                        break;
        } while (errno == EINTR);
        if (ret)
                *ret = NULL;
        return 0;
}


/*
 *  Cancel thread
 */

int pthread_cancel(pthread_t thread)
{
        kill(thread, SIGINT);
        return 0;
}


/*
 *  Test for cancellation
 */

void pthread_testcancel(void)
{
}


/*
 *  Spinlocks
 */

static int try_acquire_spinlock(int *lock)
{
        return test_and_set(lock, 1) == 0;
}

static void acquire_spinlock(volatile int *lock)
{
        do {
                while (*lock) ;
        } while (test_and_set((int *)lock, 1) != 0);
}

static void release_spinlock(int *lock)
{
        *lock = 0;
}


/*
 *  Initialize mutex
 */

int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *mutex_attr)
{
        // pthread_init_lock
        mutex->__m_lock.__status = 0;
        mutex->__m_lock.__spinlock = 0;

        mutex->__m_kind = mutex_attr ? mutex_attr->__mutexkind : PTHREAD_MUTEX_TIMED_NP;
        mutex->__m_count = 0;
        mutex->__m_owner = NULL;
        return 0;
}


/*
 *  Destroy mutex
 */

int pthread_mutex_destroy(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                return (mutex->__m_lock.__status != 0) ? EBUSY : 0;
        default:
                return EINVAL;
        }
}


/*
 *  Lock mutex
 */

int pthread_mutex_lock(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                acquire_spinlock(&mutex->__m_lock.__spinlock);
                return 0;
        default:
                return EINVAL;
        }
}


/*
 *  Try to lock mutex
 */

int pthread_mutex_trylock(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                if (!try_acquire_spinlock(&mutex->__m_lock.__spinlock))
                        return EBUSY;
                return 0;
        default:
                return EINVAL;
        }
}


/*
 *  Unlock mutex
 */

int pthread_mutex_unlock(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                release_spinlock(&mutex->__m_lock.__spinlock);
                return 0;
        default:
                return EINVAL;
        }
}


/*
 *  Create mutex attribute
 */

int pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
        attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
        return 0;
}


/*
 *  Destroy mutex attribute
 */

int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
{
        return 0;
}


/*
 *  Init semaphore
 */

int sem_init(sem_t *sem, int pshared, unsigned int value)
{
        sem->sem_lock.status = 0;
        sem->sem_lock.spinlock = 0;
        sem->sem_value = value;
        sem->sem_waiting = NULL;
        return 0;
}


/*
 *  Delete remaphore
 */

int sem_destroy(sem_t *sem)
{
        return 0;
}


/*
 *  Wait on semaphore
 */

void null_handler(int sig)
{
}

int sem_wait(sem_t *sem)
{
        acquire_spinlock(&sem->sem_lock.spinlock);
        if (sem->sem_value > 0)
                atomic_add((int *)&sem->sem_value, -1);
        else {
                sigset_t mask;
                if (!sem->sem_lock.status) {
                        struct sigaction sa;
                        sem->sem_lock.status = SIGUSR2;
                        sa.sa_handler = null_handler;
                        sa.sa_flags = SA_RESTART;
                        sigemptyset(&sa.sa_mask);
                        sigaction(sem->sem_lock.status, &sa, NULL);
                }
                sem->sem_waiting = (struct _pthread_descr_struct *)getpid();
                sigemptyset(&mask);
                sigsuspend(&mask);
                sem->sem_waiting = NULL;
        }
        release_spinlock(&sem->sem_lock.spinlock);
        return 0;
}


/*
 *  Post semaphore
 */

int sem_post(sem_t *sem)
{
        acquire_spinlock(&sem->sem_lock.spinlock);
        if (sem->sem_waiting == NULL)
                atomic_add((int *)&sem->sem_value, 1);
        else
                kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
        release_spinlock(&sem->sem_lock.spinlock);
        return 0;
}


/*
 *  Simple producer/consumer test program
 */

#ifdef TEST
#include <stdio.h>

static sem_t p_sem, c_sem;
static int data = 0;

static void *producer_func(void *arg)
{
        int i, n = (int)arg;
        for (i = 0; i < n; i++) {
                sem_wait(&p_sem);
                data++;
                sem_post(&c_sem);
        }
        return NULL;
}

static void *consumer_func(void *arg)
{
        int i, n = (int)arg;
        for (i = 0; i < n; i++) {
                sem_wait(&c_sem);
                printf("data: %d\n", data);
                sem_post(&p_sem);
        }
        sleep(1); // for testing pthread_join()
        return NULL;
}

int main(void)
{
        pthread_t producer_thread, consumer_thread;
        static const int N = 5;

        if (sem_init(&c_sem, 0, 0) < 0)
                return 1;
        if (sem_init(&p_sem, 0, 1) < 0)
                return 2;
        if (pthread_create(&producer_thread, NULL, producer_func, (void *)N) != 0)
                return 3;
        if (pthread_create(&consumer_thread, NULL, consumer_func, (void *)N) != 0)
                return 4;
        pthread_join(producer_thread, NULL);
        pthread_join(consumer_thread, NULL);
        sem_destroy(&p_sem);
        sem_destroy(&c_sem);
        if (data != N)
                return 5;
        return 0;
}
#endif
Revision:	1.4
Committed:	2004-01-04T16:27:50Z (20 years, 11 months ago) by gbeauche
Content type:	text/plain
Branch:	MAIN
Changes since 1.3:	+69 -4 lines
Log Message:	Fix pthread_join() to actually wait for children. Fix semaphores and also provide a simple producer/consumer test program.
#	Content
1	/*
2	* sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
3	* like nonstandard stacks)
4	*
5	* SheepShaver (C) 1997-2002 Christian Bauer and Marc Hellwig
6	*
7	* This program is free software; you can redistribute it and/or modify
8	* it under the terms of the GNU General Public License as published by
9	* the Free Software Foundation; either version 2 of the License, or
10	* (at your option) any later version.
11	*
12	* This program is distributed in the hope that it will be useful,
13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15	* GNU General Public License for more details.
16	*
17	* You should have received a copy of the GNU General Public License
18	* along with this program; if not, write to the Free Software
19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20	*/
21
22	/*
23	* NOTES:
24	* - pthread_cancel() kills the thread immediately
25	* - Semaphores are VERY restricted: the only supported use is to have one
26	* thread sem_wait() on the semaphore while other threads sem_post() it
27	* (i.e. to use the semaphore as a signal)
28	*/
29
30	#include <sys/types.h>
31	#include <sys/wait.h>
32	#include <stdlib.h>
33	#include <errno.h>
34	#include <unistd.h>
35	#include <signal.h>
36	#include <sched.h>
37	#include <pthread.h>
38	#include <semaphore.h>
39
40
41	/* Thread stack size */
42	#define STACK_SIZE 65536
43
44	/* From asm_linux.S */
45	extern int atomic_add(int *var, int add);
46	extern int atomic_and(int *var, int and);
47	extern int atomic_or(int *var, int or);
48	extern int test_and_set(int *var, int val);
49
50	/* Linux kernel calls */
51	extern int __clone(int (fn)(void ), void , int, void );
52
53	/* struct sem_t */
54	#define status __status
55	#define spinlock __spinlock
56	#define sem_lock __sem_lock
57	#define sem_value __sem_value
58	#define sem_waiting __sem_waiting
59
60	/* Wait for "clone" children only (Linux 2.4+ specific) */
61	#ifndef __WCLONE
62	#define __WCLONE 0
63	#endif
64
65
66	/*
67	* Return pthread ID of self
68	*/
69
70	pthread_t pthread_self(void)
71	{
72	return getpid();
73	}
74
75
76	/*
77	* Test whether two pthread IDs are equal
78	*/
79
80	int pthread_equal(pthread_t t1, pthread_t t2)
81	{
82	return t1 == t2;
83	}
84
85
86	/*
87	* Send signal to thread
88	*/
89
90	int pthread_kill(pthread_t thread, int sig)
91	{
92	if (kill(thread, sig) == -1)
93	return errno;
94	else
95	return 0;
96	}
97
98
99	/*
100	* Create pthread
101	*/
102
103	struct new_thread {
104	void (fn)(void *);
105	void *arg;
106	};
107
108	static int start_thread(void *arg)
109	{
110	struct new_thread nt = (struct new_thread )arg;
111	nt->fn(nt->arg);
112	return 0;
113	}
114
115	int pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg)
116	{
117	struct new_thread *nt;
118	void *stack;
119	int pid;
120
121	nt = (struct new_thread *)malloc(sizeof(struct new_thread));
122	nt->fn = start_routine;
123	nt->arg = arg;
124	stack = malloc(STACK_SIZE);
125
126	pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM \| CLONE_FS \| CLONE_FILES, nt);
127	if (pid == -1) {
128	free(stack);
129	free(nt);
130	return errno;
131	} else {
132	*thread = pid;
133	return 0;
134	}
135	}
136
137
138	/*
139	* Join pthread
140	*/
141
142	int pthread_join(pthread_t thread, void **ret)
143	{
144	do {
145	if (waitpid(thread, NULL, __WCLONE) >= 0);
146	break;
147	} while (errno == EINTR);
148	if (ret)
149	*ret = NULL;
150	return 0;
151	}
152
153
154	/*
155	* Cancel thread
156	*/
157
158	int pthread_cancel(pthread_t thread)
159	{
160	kill(thread, SIGINT);
161	return 0;
162	}
163
164
165	/*
166	* Test for cancellation
167	*/
168
169	void pthread_testcancel(void)
170	{
171	}
172
173
174	/*
175	* Spinlocks
176	*/
177
178	static int try_acquire_spinlock(int *lock)
179	{
180	return test_and_set(lock, 1) == 0;
181	}
182
183	static void acquire_spinlock(volatile int *lock)
184	{
185	do {
186	while (*lock) ;
187	} while (test_and_set((int *)lock, 1) != 0);
188	}
189
190	static void release_spinlock(int *lock)
191	{
192	*lock = 0;
193	}
194
195
196	/*
197	* Initialize mutex
198	*/
199
200	int pthread_mutex_init(pthread_mutex_t mutex, const pthread_mutexattr_t mutex_attr)
201	{
202	// pthread_init_lock
203	mutex->__m_lock.__status = 0;
204	mutex->__m_lock.__spinlock = 0;
205
206	mutex->__m_kind = mutex_attr ? mutex_attr->__mutexkind : PTHREAD_MUTEX_TIMED_NP;
207	mutex->__m_count = 0;
208	mutex->__m_owner = NULL;
209	return 0;
210	}
211
212
213	/*
214	* Destroy mutex
215	*/
216
217	int pthread_mutex_destroy(pthread_mutex_t *mutex)
218	{
219	switch (mutex->__m_kind) {
220	case PTHREAD_MUTEX_TIMED_NP:
221	return (mutex->__m_lock.__status != 0) ? EBUSY : 0;
222	default:
223	return EINVAL;
224	}
225	}
226
227
228	/*
229	* Lock mutex
230	*/
231
232	int pthread_mutex_lock(pthread_mutex_t *mutex)
233	{
234	switch (mutex->__m_kind) {
235	case PTHREAD_MUTEX_TIMED_NP:
236	acquire_spinlock(&mutex->__m_lock.__spinlock);
237	return 0;
238	default:
239	return EINVAL;
240	}
241	}
242
243
244	/*
245	* Try to lock mutex
246	*/
247
248	int pthread_mutex_trylock(pthread_mutex_t *mutex)
249	{
250	switch (mutex->__m_kind) {
251	case PTHREAD_MUTEX_TIMED_NP:
252	if (!try_acquire_spinlock(&mutex->__m_lock.__spinlock))
253	return EBUSY;
254	return 0;
255	default:
256	return EINVAL;
257	}
258	}
259
260
261	/*
262	* Unlock mutex
263	*/
264
265	int pthread_mutex_unlock(pthread_mutex_t *mutex)
266	{
267	switch (mutex->__m_kind) {
268	case PTHREAD_MUTEX_TIMED_NP:
269	release_spinlock(&mutex->__m_lock.__spinlock);
270	return 0;
271	default:
272	return EINVAL;
273	}
274	}
275
276
277	/*
278	* Create mutex attribute
279	*/
280
281	int pthread_mutexattr_init(pthread_mutexattr_t *attr)
282	{
283	attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
284	return 0;
285	}
286
287
288	/*
289	* Destroy mutex attribute
290	*/
291
292	int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
293	{
294	return 0;
295	}
296
297
298	/*
299	* Init semaphore
300	*/
301
302	int sem_init(sem_t *sem, int pshared, unsigned int value)
303	{
304	sem->sem_lock.status = 0;
305	sem->sem_lock.spinlock = 0;
306	sem->sem_value = value;
307	sem->sem_waiting = NULL;
308	return 0;
309	}
310
311
312	/*
313	* Delete remaphore
314	*/
315
316	int sem_destroy(sem_t *sem)
317	{
318	return 0;
319	}
320
321
322	/*
323	* Wait on semaphore
324	*/
325
326	void null_handler(int sig)
327	{
328	}
329
330	int sem_wait(sem_t *sem)
331	{
332	acquire_spinlock(&sem->sem_lock.spinlock);
333	if (sem->sem_value > 0)
334	atomic_add((int *)&sem->sem_value, -1);
335	else {
336	sigset_t mask;
337	if (!sem->sem_lock.status) {
338	struct sigaction sa;
339	sem->sem_lock.status = SIGUSR2;
340	sa.sa_handler = null_handler;
341	sa.sa_flags = SA_RESTART;
342	sigemptyset(&sa.sa_mask);
343	sigaction(sem->sem_lock.status, &sa, NULL);
344	}
345	sem->sem_waiting = (struct _pthread_descr_struct *)getpid();
346	sigemptyset(&mask);
347	sigsuspend(&mask);
348	sem->sem_waiting = NULL;
349	}
350	release_spinlock(&sem->sem_lock.spinlock);
351	return 0;
352	}
353
354
355	/*
356	* Post semaphore
357	*/
358
359	int sem_post(sem_t *sem)
360	{
361	acquire_spinlock(&sem->sem_lock.spinlock);
362	if (sem->sem_waiting == NULL)
363	atomic_add((int *)&sem->sem_value, 1);
364	else
365	kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
366	release_spinlock(&sem->sem_lock.spinlock);
367	return 0;
368	}
369
370
371	/*
372	* Simple producer/consumer test program
373	*/
374
375	#ifdef TEST
376	#include <stdio.h>
377
378	static sem_t p_sem, c_sem;
379	static int data = 0;
380
381	static void producer_func(void arg)
382	{
383	int i, n = (int)arg;
384	for (i = 0; i < n; i++) {
385	sem_wait(&p_sem);
386	data++;
387	sem_post(&c_sem);
388	}
389	return NULL;
390	}
391
392	static void consumer_func(void arg)
393	{
394	int i, n = (int)arg;
395	for (i = 0; i < n; i++) {
396	sem_wait(&c_sem);
397	printf("data: %d\n", data);
398	sem_post(&p_sem);
399	}
400	sleep(1); // for testing pthread_join()
401	return NULL;
402	}
403
404	int main(void)
405	{
406	pthread_t producer_thread, consumer_thread;
407	static const int N = 5;
408
409	if (sem_init(&c_sem, 0, 0) < 0)
410	return 1;
411	if (sem_init(&p_sem, 0, 1) < 0)
412	return 2;
413	if (pthread_create(&producer_thread, NULL, producer_func, (void *)N) != 0)
414	return 3;
415	if (pthread_create(&consumer_thread, NULL, consumer_func, (void *)N) != 0)
416	return 4;
417	pthread_join(producer_thread, NULL);
418	pthread_join(consumer_thread, NULL);
419	sem_destroy(&p_sem);
420	sem_destroy(&c_sem);
421	if (data != N)
422	return 5;
423	return 0;
424	}
425	#endif